Cartridge protectors for modular connector blocks are known in the art, for example, from U.S. Pat. No. 5,627,721. The individual pairs of telephone circuit wires, for example, are frequently terminated in telephone company central offices and customer premises utilizing multi-terminal connector blocks. Once terminated, these telephone circuit wires, usually comprised of narrow gauge insulated copper cables, are grouped and then rerouted for appropriate distribution of the calls that they carry. Single connector blocks normally accommodate anywhere from sixty to one-hundred pairs of densely packed terminations, wherein multiple connector blocks are frequently contained in close proximity at a single location, for example, one wall of a telephone switching room. Efficient utilization of mounting space is thus required because space within utility locations is traditionally at a premium.
Protective circuitry is a typical accessory circuit that may be connected to the connector blocks. In the art of telecommunications equipment, for example, it is known to provide protective circuits to protect delicate circuitry, including line cards, switching circuits, multiplexers and the like at a central office or other location from overload conditions that may result, for example, from a lightning strike or fallen high-voltage line.
In a conventional manner, a protective circuit in the form of a cartridge or pair-at-a-time module is mounted within a slot of the connector block which may be associated with one or more communication lines. The mounted protector circuit is inserted in the communication circuit, typically between the contacts of opposing IDC connectors to thereby interpose the protective circuit on an unprotected side of the line. The protector circuit provides a ground path during an overload condition to protect the telecommunication circuit.
It is generally desirable to provide a protective circuit which can withstand transient energy strikes, e.g., due to lightning. A greater ability to withstand momentary overload conditions results in fewer service calls to inspect, reset, or replace components on the line. Overload protection is typically configured to protect against over-voltages and over-currents (sometimes referred to as "sneak" currents).
Unfortunately, the capacity of voltage overload protection devices is directly related to the size of the device. Thus, a conventional 6 mm (0.236") gas tube overvoltage protector does not have as great a withstand capability as a conventional 8 mm (0.315") protector. The space constraints at the terminal blocks have dictated a lower capacity rating than might otherwise have been desired for a given application. High-density connecting systems such as the high-density Z-IDC connector block provided by Lucent Technologies, Inc. of Murray Hill, N.J., has a 0.300" (&lt;8 mm) spacing between adjacent lines, and so 8 mm gas tubes have not been used in such high-density systems. Instead, such systems have used 6 mm gas tubes, although the 8 mm might have been preferred for a particular application.
The space constraints imposed by the line spacing of the standard connector blocks has restricted the capacity and number of components used in the associated protective circuitry. What is needed in the art and has heretofore not been available is a cartridge protector for a high-density system which overcomes the problems of prior art cartridge protectors. What is further needed in the art and has not heretofore been available is such a cartridge protector which provides a more optimum overload protection within the space constraints imposed by conventional connector blocks.